Method of magnetically shrink-fitting members

ABSTRACT

Magnetostrictive fastener arrangement that relies upon the fractional change in length of a ferromagnetic element under the influence of a magnetic field (magnetostriction) to alter the physical cooperating relationship between the element and a second element. Each of the elements may exhibit the same or a different magnetostrictive effect in the presence of a magnetic field, and each of the elements is dimensioned so that a different physical relationship between the elements is achieved when either or both elements undergoes a fractional change in length.

United States Patent [191 Beer [ METHOD OF MAGNETICALLY SHRINK-FITTINGMEMBERS Inventor: Andrew E. Beer,25 Sutt on Place,

New York, NY. 10022 Filed: Sept. 19, 1972 Appl. No.: 290,349

[52] US. Cl 29/446, 29/426, 29/526, 52/204, 114/116, 227/156, 285/381,

Int. Cl B23p 11/02 Field of Search..... 29/421 M, 446, 447, 426 X,29/526 X; 335/215 X; 227/156 X; 285/381 X; 52/204 X; 114/116 X; 403/273X [56] References Cited UNITED STATES PATENTS 3/1948 Rockwell et a1.29/446 UX 7/1959 Marx 325/215 X 12/1965 Schwinghamer 29/421 M X3,345,732 10/1967 Brower 29/421 M 3,718,957 3/1973 Shank 29/447 XFOREIGN PATENTS OR APPLICATIONS 597,743 5/1960 Canada 335/215 June 18,1974 OTHER PUBLICATIONS Magnetostriction PhenomenaGeneral Review-Vol.45, No. 3, pp. 161-163.

Electric Primary Examiner-Charlie T. Moon Attorney, Agent, orFirm-Brumbaugh, Graves, Donohue & Raymond Magnetostrictive fastenerarrangement that relies upon the fractional change in length of aferromagnetic element under the influence of a magnetic field(magnetostriction) to alter the physical cooperating relationshipbetween the element and a second element. Each of the elements mayexhibit the same or a different magnetostrictive effect in the presenceof a magnetic field, and each of the elements is dimensioned so that adifferent physical relationship between the elements is achieved wheneither or both elements undergoes a fractional change in length.

ABSTRACT 14 Claims, 15 Drawing Figures PAIENTEuJuuIamm 3816.902

SHEET 1 0F 3 x 0% 0% I20 X 650 350 MAGNETOSTRICTION, IN INCHES 1 I 1 l II 1 I O 400 800 I200 I600 2000 MAGNETIC FIELD STRENGTH, H, IN OERSTEDSPATENTEDJus 18 am y 3316.902

sum 2 or 3 FIG. 7

METHOD OF MAGNETICALLY SHRINK-FITTING MEMBERS BACKGROUND OF THEINVENTION This invention relates to an improvement in fasteningarrangements and more particularly, to magnetostrictive fasteners thatutilize the principle of magnetostriction to provide enhanced holdingaction.

Fasteners, such as screws, nails, studs, rivets, nuts and bolts and thelike are well known and extensively used to join materials together.Such fasteners tend to loosen, however, especially where the materialsjoined together undergo stresses and strains. Also, certain types offasteners are subject to corrosion. Such corrosion action may cause thefastener to loosen because of the reduction in its size or, may make thefastener difficult to take apart which is necessary in the normalmaintenance of machinery. Thermal expansion of metals has been utilizedto provide long term tightfitting fasteners. For example, pipeconnections are commonly made by joining preheated and precooled pipes.There are practical difficulties in applying the principle in otherfastening arrangements. The heating equipment needed to provide therequired temperature changes may be bulky and non-portable. Also,certain elements to be secured, such as large metal pieces, may notreadily change their ambient temperature.

Therefore, a fastening arrangement that would fit tightly by changingdimensions at the time of assembly or disassembly while at the same timenot requiring extensive, additional equipment would be a valuableadvance in the art of fasteners.

SUMMARY OF THE INVENTION There is provided in accordance with thepresent invention a fastener arrangement that overcomes the problemsmentioned previously. More particularly, the invention relates to afastening arrangement wherein at least one element of the fastener is atleast partially made of a magnetostrictive material that undergoes shapechanges in the presence of a magnetic field. Each of the elements is sodimensioned that a different physical relationship between the elementsis implemented when either or both magnetostrictive elements undergoes afractional change in length in the presence of a magnetic field ofappropriate strength.

Where the fastener is a magnetostrictive screw, nail, stud, rivet, bolt,washer, electrical connector or the like, removal of the magnetic fieldafter the fastener is in place causes an increase in the diameter of thefastener. The result is that the fastener fits more securely in thereceiving holes in the elements to be held together. Thus, the fit ismore snug than with conventional fasteners. The term fastener is meantto include any type of arrangement where parts may be made rigid withrespect to each other. Also, a cotter pin may be made in part of amagnetostrictive material so that the application of a magnetic fieldcauses the shaft of the pin to curve or be straight.

Corrosion may be reduced by fashioning the fastener of amagnetostrictive material that has less tendency to rust. Moreimportantly, since the fit is more snug than conventional fasteners,there is less tendency for corrosion because oxygen has less surfacearea in which to oxidize. In addition, the usual difficulty in removingcorroded fasteners is minimized by the use of magnetostrictivefasteners. To remove the fastener, a magnetic field is applied tothereby decrease the diameter of the fastener and thereby crack anycorroded surface that may be present.

In another form of the invention the fastener may be a magnetostrictivechuck for holding a machine tool in place or alternatively, the toolitself may be made of a magnetostrictive material. Additionally, doorswith magnetostrictive lining may be used to form a tight fittingfastening arrangement.

The additional equipment needed to cause the enhanced fastening actionconsists of a suitable source of a magnetic field. Either smallpermanent magnets or electromagnets may be used. In some cases thedevice used to insert the fastener into place, such as a screw driver orwrench, etc., may be modified so as to also incorporate the source ofthe magnetic field.

BRIEF DESCRIPTION OF THE DRAWINGS For a better understanding of theinvention, reference may be made to the following descriptions of theexemplary embodiments taken in conjunction with the following drawingsin which:

FIG. 1 is a graph showing properties of some magnetostrictive materials;

FIG. 2 is a schematic of a magnetostrictive nut and bolt combinationarranged according to the present invention;

FIG. 3 is a sectional view of magnetostrictive nut and bolt in placearranged according to the present invention;

FIG. 4 is a sectional view of magnetostrictive rivet in place;

FIG. 5 is a sectional view of magnetostrictive nail in place;

FIG. 6 is a sectional view of a magnetostrictive screw in place;

FIG. 7 is a view of a magnetostrictive pipe connection;

FIG. 8 is a magnetostrictive can arranged according to the presentinvention;

FIG. 9 is a magnetostrictive fitting arranged according to the presentinvention;

FIG. 10 is a sectional view of a magnetostrictive stud arrangedaccording to the present invention;

FIG. 11a is a partial sectional view of a machine tool held by a chuckarranged according to the present invention;

FIG. 11b is a view of the machine tool and chuck taken along lines 11bof FIG. 11a;

FIG. 12 is a view of a magnetostrictive door arranged according to thepresent invention;

FIG. 13 is a view of a bolt and magnetostrictive washer arrangedaccording to the present invention;

FIG. 14 is a view of a magnetostrictive cotter pin arranged according tothe present invention.

In the following descriptions of illustrative embodiments ofmagnetostrictive devices arranged according to the present invention,all are based on the novel application of the principle ofmagnetostriction.

PRINCIPLES OF MAGNETOSTRICTION Magnetostriction refers to the fractionalchange in length of a ferromagnetic body under the influence of amagnetic field. The three main kinds of magnetostriction arelongitudinal magnetostriction, transverse magnetostriction and volumemagnetostriction. Longitudinal magnetostriction may be either positive(Fe-Co Alloys) or negative (Ni and Co) or may be positive (elongate withincreasing field) at low fields and negative for large fields.Transverse magnetostriction is measured orthogonally to the field andgenerally is equal to one half the longitudinal magnetostriction and ofopposite sign. Volume magnetostriction is generally an order ofmagnitude smaller than longitudinal magnetostriction.

While all ferromagnetic materials have magnetostrictive qualities, theiron cobalt alloys (Fe-Co) appear to produce the greatest effect. Thecurves of FIG. 1 indieative magnetostriction as a function of fieldstrength for three cold rolled Fe-Co alloys; for the Fe 30 Co 70 alloy,the magnetostriction is 1.2 X in./in. at a field strength of 1,000oersteds. The thermal expansion for the same alloy for a 100F.temperature change is 6 X 10" in./in.

Since the greatest amount of magnetostriction occurs as the materialapproaches saturation, the magnet for producing the field must becapable of producing a large enough field. The magnetostrictivematerials utilized in the present invention, such as the Fe-Co alloys,generally do not require more than 1,000 oersteds to saturate them. Whenthe alloys are not cold rolled, 200 oersteds may be sufficient. However,the shape of the magnetostrictive material, which determines thedemagnetization factor, may necessitate the use of a much larger fieldto ensure the magnetostrictive material is near saturation.

Permanent magnets are suitable in most applications for generating themagnetic fields necessary to cause magnetostriction. Depending on'theapplication of the magnetostrictive material, various shaped permanentmagnets are available, such as horseshoe, bar, circular or rod,depending on the direction of the magnetic field required in relation tothe structure of the magnetostrictive material. Ceramic magnets, such asbarriumferrite, are readily available and provide field strengths from2,000 to 3,000 oersteds. Also, Alnico permanent magnets provide the samerange of field strength. In some applications it may be desirable tohave higher field strengths. The rare earth cobalt alloy magnets, suchas platinum cobalt, provide field strengths in excess of 3,000 oersteds.

Most permanent magnets provide the previously mentioned field strengthsin a relatively small volume of air. Therefore, where themagnetostrictive material is relatively large, electromagnets with orwithout an iron return circuit may be used. Air coils provide fieldstrengths of the order of 1,000 oerstedsv over a large volume. Wherehigher fields are desirable, electromagnets with an iron return circuitgenerate field strengths to 5,000 oersteds in a one inch air gap.Electromagnets maybe useful when the present invention is utilized inindustrial applications. I

PREFERRED EMBODIMENTS In the illustrative embodiment of amagnetostrictive fastening arrangement according to the presentinvention, as. shown in FIG. 2, there is provided a nut and boltcombination for securing elements (not' shown) together. In the drawing,a bolt 10 with a head 11 and external threads 12 and an internallythreaded nut 14 are designed for engaging relationship. Withconventional nut and bolt combinations, the inside diameter of the nutis somewhat larger than the outside diameter of the bolt so that the twomay be readily joined together. Friction between the elements joinedtogether and the bolt and nut respectively is relied upon to maintain atight connection. However, in the presentinvention, the bolt 10 is madeof a magnetostrictive material, such as a Fe-Co alloy, with an outsidediameter that is approximately equal to the inside diameter of the bolt.In this condition the two may not be readily joined or if joined,separated.

A magnetic field is applied to the bolt 10 in a direction parallel toits axis when the combination is to be assembled or separated. This maybe provided by an electromagnetic surrounding the bolt, a speciallydesigned tool or, where appropriate, by a permanent magnet shaped as ahorseshoe with one pole near the head 11 of the bolt 10 and the otherpole near the nut 14. The magnetic field causes the length of the boltto increase and the diameter to decrease about half the increase inlength. After the combination is assembled and the field removed, thebolt 10 reassumes its original shape. The transverse magnetostriction,along the diameter, causes the nut and bolt to fit securely. In someapplications it may be desirable to have the nut 14 made of amagnetostrictive material.

In FIG. 3, there is shown a sectional view of the bolt 10 and nut 14holding a pair of elements 16 and 18 in place. Not only does transversemagnetostriction enhance the holding action, but also, longitudinalmagnetostriction provides a tighter fit. Since the length of the bolt 10increases when a magnetic field is present, the removal of the fieldafter assembly causes the bolt 10 to decrease its length and therebycauses greater holding pressure to be exerted on the elements 16 and 18.Alternatively, the bolt 10 and the nut 14, instead of being formed withthreads, may have smooth engaging surfaces.

FIG. 4, indicates a magnetostrictive fastener in the form of a rivet 20.A pair of elements 22 and 24 with matching holes receive the rivet 20.The diameter of the rivet 20 is larger than the diameter of the holes ofthe members 22 and 24. A magnetic field, applied parallel to the lengthof the rivet 20, by a device similar to that described in FIG. 2,decreases the diameter so that it may be inserted into the bores in theelements 22 and 24. The head 20a is then'formed on the rivet in theusual manner, and when the field is removed, the diameter of the rivet20 increases while its length decreases, thereby to hold the elements 20and 24 in tighter relationship.

As shown in FIG. 5, a nail 30 with a head 32 and a shaft 34 is made of amagnetostrictive material. When the nail 30 is to be driven into anelement 36, such as wood, a magnetic field is provided parallel to theshaft of the nail 30, thereby decreasing the diameter of the nail. Afterthe nail 30 is driven into the wood 36, the magnetic field is removed toincrease the diameter of the nail 30.

In similar manner, there is shown in FIG. 6 a magnetostrictive screw 40.The screw 40 with threads 42 is made of a magnetostrictive material andis shown seated in an element 44, such as wood or metal. The screw isinserted while the magnetic field is applied parallel to the shafi ofthe screw 40. The result of this action, again after the field has beenremoved, is that the screw fits more securely into the material 44because of its increased diameter. The magnetostrictive screw 40, alongwith the other fastening arrangements, have the advantageous feature offacilitating their removal if any corrosion should accumulate on thefasteners over long time periods. The change in size of the fastenerscan cause the corrosion, including rust, to break loose.

Referring to FIG. 7, there is shown an improved pipe connection arrangedaccording to the present invention. A pipe 52 has a coupling section 54adapted at one end to receive the end of another pipe 56. In the presentinvention, an end 57 of the pipe 56 is made of a magnetostrictivematerial with a diameter approximating the internal diameter of thecoupling 54. When the pipes are to be fitted together, a magnetic fieldis applied parallel to the length of the pipe 56 which causes the end 57of the pipe to contract, as shown in FIG. 7, so as to allow the pipe 56to be inserted into the coupling 54. After the magnetic field isremoved, the diameter of the end 57 of the pipe 56 increases to cause atight fitting pipe connection.

Referring now to FIG. 8, a can 56 has a top member 58 formed ofmagnetostrictive material frictionally secured within the recess of aninterior lip 60 of the can. A permanent magnet 62 is located adjacentthe top 58 to generate a magnetic field perpendicular to the surface ofthe top 58. The magnetic field causes the diameter of the top 58 todecrease thereby causing the top member 58 to separate from the lip 60.The top member 58 adheres to the magnet 62 after removal from the can56.

In a fitting arranged according to the present invention as shown inFIG. 9, a bar 66 is joined with another bar 68 by means of a fitting 70.Ends 67 and 69 of the bars 66 and 68, respectively, are made of amagnetostrictive material, and have a diameter slightly greater thaninner diameter 72 of the fitting 70. When joining the rods 66 and 68, amagnetic field parallel to the axis of the rods causes the diameter ofthe ends 67 and 69 of the rods 66 and 68, respectively, to decrease, asshown in FIG. 9, so that the rods fit into the fitting 70. When thefield is removed, therods are held by the fitting 70.

Referring now to FIG. 10, a threaded stud 74 made of a magnetostrictivematerial is engaged with a nut 76 to hold the elements 78 and 80together. The external threads of the stud 74 match the internal threadsof the element 80. Similarly, as in the nut and bolt combination showninFIG. 3, the holding action of the stud is enhanced by bothlongitudinal and transverse magnetostriction. Also, the stud 74, nut 76and element 80 may be formed without threads.

FIG. 11a and FIG. 11b show the application of the principle ofmagnetostriction to a chuck adapted to hold a machine tool 82, having aworking end 84 and a securing end 86, is held by a chuck, representedgenerally by the reference numeral 88. In one manner of holding the tool82 in place in the chuck 88, the securing end 86 is placed in areceiving hole 90 in the chuck 88 formed by a series of three arcuateadjustable chuck sections 92, 94 and 96. The inner edges of the sections92, 94 and 96 fonn the receiving hole 90 and by conventional adjustmenttechniques (not shown) these sections may releasably grip the securingend 86 of the tool 82. The present invention may either supplement oreliminate the adjustment techniques.

In one form of the invention the sections 92, 94 and 96 are formed of amagnetostrictive material. Thus, when it is desired to insert the tool82 into the chuck 88, a magnetic field, which may be provided by eithera permanent magnet or electromagnet, is applied to the sections 92, 94and 96 to cause them to alter their size and thereby increase the sizeof the receiving hole to allow the securing end 86 to be inserted, asshown in FIG. 11a and FIG. 11b. The magnetic field is then removed whichcauses the sections to alter their dimensions so that they securely gripthe tool 82. The sections may also be adapted to hold the tool when amagnetic field is applied to them and release the tool when the field isremoved. In this form, it may be more suitable to have the fieldproducing means be an appropriate electromagnet that is permanentlyaffixed to the chuck. Control of the tool may then be accomplished bycontrolling electrical power to the electromagnet as with a switch.

In another form of the invention the securing end 86 of the tool 82 maybe formed of a magnetostrictive material with the receiving hole 90being of conventional design. To insert the tool 82 into the chuck 88 amagnetic field is applied to the securing end 86 to alter its dimensionsto cause it to fit into the chuck. When the field is removed, the toolassumes its original shape which results in the tool being firmly heldby the chuck.

Referring now to FIG. 12 a door 100 is mounted on a wall 102 by a pairof hinges 104. The shape of the door is not critical and may be squareas shown, rectangular, or circular as with portholes on ships. Mountedaround the perimeter of the door 100 is a strip 106 of magnetostrictivematerial. To close the door 100 a magnetic field is applied to the strip106 to cause the strip to alter its size and thereby slightly decreasethe overall perimeter of the door 100. The door 100 may then be swunginto engagement with the wall 102. The removal of the magnetic fieldcauses the strip 106 to assume its original dimensions which cause thedoor to fit snugly within the wall. In an alternative form of thisembodiment, the strip 106 of magnetostrictive material may be placedalong the edges of the opening in the wall 102. The tight fittingarrangement forms an excellent barrier for preventing leakage of wateror air and thus is applicable for use in ships and space vehicles wheretight fitting passageways are of utmost importance. The magnet may beprotable or permanently mounted within either the door or wall.

In FIG. 13 a bolt 110, having a head 112 and a shaft 114, is adapted tobe inserted into an aperture 115 in a receiving member 116. A washer 118made of a magnetostrictive material is rigidly mounted on the shaft 114of the bolt due to the magnetostrictive principle. An outermost portion120 of the receiving part 116 is also made of a magnetostrictivematerial. To insert the bolt 110 into the aperture 115 of the receivingpart 116 a magnetic field is applied to the washer 118 and the outermostpart 120 which causes the magnetostrictive materials to alter theirdimensions. Removing the magnetic field causes the magnetostrictivematerials to assume their original dimensions, the result being that thewasher 118 is too large to fit through the aperture formed by theoutermost portion 120. Thus, the bolt is secured within the receivingpart and may not be removed until a magnetic field is applied to themagnetostrictive material. In some applications it may be desirable tohave only the washer 118 or only the outermost portion 120 made of amagnetostrictive material.

Referring now to FIG. 14, a receiving part 122 has an aperture l24'withan outwardlyflaring end section 126.

A cotter pin 128 has a head 130, and a shaft 132 with section 133 of theshaft being made of a magnetostrictive material. The shaft 132 is curvedas shown in FIG. 14 absent any magnetic field. By applying a magneticfield to the cotter pin, the shaft 132 becomes straight (not shown)whereby the pin may be removed from or inserted into the receiving part122. Thus the curved shaft 132 in conjunction with the shape of the endsection 126 of the aperture 124 causes the combination of the cotter pin128 and receiving part 122 to be held in tight frictional relationship.

The present invention is applicable to increasing the frictional holdingrelationship between electrical connectors, such as electricalconnectors that are inserted into switchboards. For instance, in FIG. 14the cotter pin 128 may be an electrically conductive connector that maybe inserted into the aperture 124 which may be a receiving hole on aswitchboard. Similarly, the embodiments shown in FIG. 9 and FIG. 13 maybe modified for use as electrical connectors.

The embodiments of the present invention described previously areintended to be merely exemplary and those skilled in the art will beable to make numerous variations and modifications without departingfrom the spirit of the present invention. All such variations andmodifications are intended to be in the scope of the invention asdefined in the appended claims.

I claim:

1. A method of engaging elements in cooperating physical relationship atleast one of which is formed of magnetostrictive material comprising thesteps of applying a magnetic field to the magnetostrictive element tochange a dimension thereof and alter the physical cooperatingrelationship between the elements, securing the elements together in africtional engagement, and removing the magnetic field to cause afractional change in a dimension of the element and provide a greaterfrictional engagement between the elements to lock them together moresecurely.

2. The method according to claim 1, wherein the magnetostrictive elementis a nail adapted to be driven into and engage the second element in thepresence of the magnetic field, the diameter of the nail decreasing whenthe magnetic field is applied parallel to the axis of the nail, wherebythe diameter of the nail increases in the absence of the magnetic fieldto provide a greater frictional locking relationship between the nailand the second element.

3. The method according to claim 1, wherein the magnetostrictive elementis a screw adapted to be driven into and engage the second element inthe presence of the magnetic field, the diameter of the screw decreasingwhen the magnetic field is applied parallel to the axis of the screw,whereby the diameter of the screw increases in the absence of themagnetic field to provide a greater frictional locking relationshipbetween the screw and the second element.

4. The method according to claim 1, wherein the magnetostrictive elementis a rivet adapted to be formed into engagement with other elements inthe presence of the magnetic field, the diameter of the rivet decreasingwhen the magnetic field is applied parallel to the axis of the rivet andwhereby the diameter of the rivet increases in the absence of themagnetic field to provide a tighter engagement between the rivet and theother elements.

5. The method according to claim 1, wherein the magnetostrictive elementis a stud adapted to be inserted into and engage other elements in thepresence of the magnetic field, the diameter of the stud decreasing whenthe magnetic field is applied generally parallel to the axis of thestud, whereby the diameter of the stud increases in the absence of themagnetic field to provide a greater frictional locking relationshipbetween the stud and the other elements.

6. The method according to claim 1, wherein the magnetostrictive elementis a pipe adapted to be inserted into another pipe having a couplingsection, the diameter of the pipe decreasing when the magnetic field isapplied parallel to the axis of the pipe whereby the diameter of thepipe increases in the absence of the magnetic field to provide a greaterfrictional locking relationship between the pipes.

7. The method according to claim 1, wherein the magnestrictive elementis a bolt and another element is a nut, the bolt adapted to engage thenut in the presence of the magnetic field, the diameter of the boltdecreasing when the magnetic field is applied parallel to the axis ofthe bolt, whereby the diameter of the bolt increases in the absence ofthe magnetic field to provide a greater frictional locking relationshipbetween the bolt and the nut.

8. The method according to claim 1, wherein the magnetostrictive elementis a bar and another element is a fitting, the bar adapted to engage thefitting in the presence of the magnetic field, the diameter of the bardecreasing when the magnetic field is applied parallel to the axis ofthe bar, whereby the diameter of the bar increases in the absence of themagnetic field to provide a greater frictional locking relationshipbetween the fitting and the bar.

9. The method according to claim 1 wherein the magnetostrictive elementcomprises a clutch formed with a receiving hole and another elementcomprises a machine tool, the machine tool adapted to engage thereceiving hole of the chuck in the presence of the magnetic field, thereceiving hole increasing in size when the magnetic field is applied,whereby the size of the receiving hole decreases in the absence of themagnetic field to provide a greater frictional locking relationshipbetween the chuck and the machine tool.

10. The method according to claim 1, wherein the magnetostrictiveelement comprises a machine tool and another element comprises a chuckformed with a receiving hole, the machine tool adapted to be engaged bythe receiving hole in the chuck, the dimensions of the tool decreasingwhen the magnetic field is applied to the tool, whereby the dimensionsof the tool increases in the absence of the magnetic field to provide agreater frictional locking relationship: between the machine tool andthe chuck.

11. The method according to claim 1, wherein the magnetostrictiveelement comprises a door having a lining made of magnetostrictivematerial formed around the perimter of the door and another elementcomprises a wall having an opening for the door, the size of the doordecreasing when the magnetic field is applied to the door, whereby thesize of the door increases in the absence of the magnetic field toprovide a greater frictional locking relationship between the door andthe wall.

12. The method according to claim 1, wherein the magnetostrictiveelement comprises a wall with an opening having a lining made ofmagnetostrictive material and another element comprises a door, the sizeof the opening increasing when the magnetic field is applied to thelining, whereby the opening decreases in the absence of the magneticfield to provide a greater frictional locking relationship between thedoor and the wall.

13. The method according to claim 1, wherein the magnetostrictiveelement comprises a washer, another element comprises a bolt adapted tobe mounted within the washer and another element comprises a receivingmember having an aperture, the size of the washer decreasing when themagnetic field is applied to the washer, whereby the size of the washerincreases in the absence of the magnetic field to provide a greaterfriccotter pin and the receiving part.

UNITED STATES PATENT OFFICE a 9 CERTIFICATE OF CORRECTION Patent No. l6,02 Dated June 1974 Inventor(s) Andrew Bpp'r It is certified that errorappears in the above-identified patent and that said Letters Patent arehereby corrected as shown below:

r- '1 Col. 3, lines 12 and 13, "indicative" should read indicate--; col.4, line 49, "20" should read --22-; col. 5, line 39, "therods" shouldread the rods; line 52, after "tool" insert A machine tool--; col. 6,line 43, "protable" should read portable-; col. 8, line 17,"magnestrictive" should read -magnetostrictive; line 35, "clutch" shouldread -chuck-; line 57, "perimter" should read -perimeter-.'

Signed and sealed this 8th day of October 1974.

(SEAL) Attest:

McCOY M. GIBSON JR. C. MARSHALL DANN Attesting Officer Commissioner ofPatents *zgigg UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTIONPatent No. r 02 Dated June 1974 Inventor-(s) Andrew E 1399? It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

Col. 3 lines 12 and 13, "indicative" should read indicate--; col. 4,line 49, "20" should read -22; col. 5, line 39, "therods" should readthe rods-; line 52, after "cool" insert A machine tool--; col. 6, line43, "protable" should read -portable-; col. 8, line 17, "magnestrictive"should read --magnetostrictive--; line 35, "clutch" should read--chuck--; line 57, "perimter" should read --perimeter---.

Signed and sealed this 8th day of October 1974.

(SEAL) Attest: I

MCCOY M. GIBSON JR. C. MARSHALL DANN Attesting Officer Commissioner ofPatents

1. A method of engaging elements in cooperating physical relationship atleast one of which is formed of magnetostrictive material comprising thesteps of applying a magnetic field to the magnetostrictive element tochange a dimension thereof and alter the physical cooperatingrelationship between the elements, securing the elements together in africtional engagement, and removing the magnetic field to cause afractional change in a dimension of the element and provide a greaterfrictional engagement between the elements to lock them together moresecurely.
 2. The method according to claim 1, wherein themagnetostrictive element is a nail adapted to be driven into and engagethe second element in the presence of the magnetic field, the diameterof the nail decreaSing when the magnetic field is applied parallel tothe axis of the nail, whereby the diameter of the nail increases in theabsence of the magnetic field to provide a greater frictional lockingrelationship between the nail and the second element.
 3. The methodaccording to claim 1, wherein the magnetostrictive element is a screwadapted to be driven into and engage the second element in the presenceof the magnetic field, the diameter of the screw decreasing when themagnetic field is applied parallel to the axis of the screw, whereby thediameter of the screw increases in the absence of the magnetic field toprovide a greater frictional locking relationship between the screw andthe second element.
 4. The method according to claim 1, wherein themagnetostrictive element is a rivet adapted to be formed into engagementwith other elements in the presence of the magnetic field, the diameterof the rivet decreasing when the magnetic field is applied parallel tothe axis of the rivet and whereby the diameter of the rivet increases inthe absence of the magnetic field to provide a tighter engagementbetween the rivet and the other elements.
 5. The method according toclaim 1, wherein the magnetostrictive element is a stud adapted to beinserted into and engage other elements in the presence of the magneticfield, the diameter of the stud decreasing when the magnetic field isapplied generally parallel to the axis of the stud, whereby the diameterof the stud increases in the absence of the magnetic field to provide agreater frictional locking relationship between the stud and the otherelements.
 6. The method according to claim 1, wherein themagnetostrictive element is a pipe adapted to be inserted into anotherpipe having a coupling section, the diameter of the pipe decreasing whenthe magnetic field is applied parallel to the axis of the pipe wherebythe diameter of the pipe increases in the absence of the magnetic fieldto provide a greater frictional locking relationship between the pipes.7. The method according to claim 1, wherein the magnestrictive elementis a bolt and another element is a nut, the bolt adapted to engage thenut in the presence of the magnetic field, the diameter of the boltdecreasing when the magnetic field is applied parallel to the axis ofthe bolt, whereby the diameter of the bolt increases in the absence ofthe magnetic field to provide a greater frictional locking relationshipbetween the bolt and the nut.
 8. The method according to claim 1,wherein the magnetostrictive element is a bar and another element is afitting, the bar adapted to engage the fitting in the presence of themagnetic field, the diameter of the bar decreasing when the magneticfield is applied parallel to the axis of the bar, whereby the diameterof the bar increases in the absence of the magnetic field to provide agreater frictional locking relationship between the fitting and the bar.9. The method according to claim 1 wherein the magnetostrictive elementcomprises a clutch formed with a receiving hole and another elementcomprises a machine tool, the machine tool adapted to engage thereceiving hole of the chuck in the presence of the magnetic field, thereceiving hole increasing in size when the magnetic field is applied,whereby the size of the receiving hole decreases in the absence of themagnetic field to provide a greater frictional locking relationshipbetween the chuck and the machine tool.
 10. The method according toclaim 1, wherein the magnetostrictive element comprises a machine tooland another element comprises a chuck formed with a receiving hole, themachine tool adapted to be engaged by the receiving hole in the chuck,the dimensions of the tool decreasing when the magnetic field is appliedto the tool, whereby the dimensions of the tool increases in the absenceof the magnetic field to provide a greater frictional lockingrelationship between the machine tool and the chuck.
 11. The methodaccording to claim 1, wherein tHe magnetostrictive element comprises adoor having a lining made of magnetostrictive material formed around theperimter of the door and another element comprises a wall having anopening for the door, the size of the door decreasing when the magneticfield is applied to the door, whereby the size of the door increases inthe absence of the magnetic field to provide a greater frictionallocking relationship between the door and the wall.
 12. The methodaccording to claim 1, wherein the magnetostrictive element comprises awall with an opening having a lining made of magnetostrictive materialand another element comprises a door, the size of the opening increasingwhen the magnetic field is applied to the lining, whereby the openingdecreases in the absence of the magnetic field to provide a greaterfrictional locking relationship between the door and the wall.
 13. Themethod according to claim 1, wherein the magnetostrictive elementcomprises a washer, another element comprises a bolt adapted to bemounted within the washer and another element comprises a receivingmember having an aperture, the size of the washer decreasing when themagnetic field is applied to the washer, whereby the size of the washerincreases in the absence of the magnetic field to provide a greaterfrictional locking relationship between the bolt and the receivingmember.
 14. The method according to claim 1, wherein themagnetostrictive element comprises a normally curved cotter pin,partially formed of a magnetostrictive material, and another elementcomprises a receiving part having an aperture, the pin becoming straightwhen the magnetic field is applied to the magnetostrictive material ofthe cotter pin, whereby the length of the pin curves in the absence ofthe magnetic field to provide a greater frictional locking relationshipbetween the cotter pin and the receiving part.